30 ATR 421 - User manual  
9.1  Slave
ATR421-12ABC-T can operate as slave unit setting di s . on parameter 77 
rem .s.: this function  allows to control multiple controllers connected to a 
supervisory system. Each instrument will answer to a Master query only if 
contains same address as on parameter 80 
sL. ad. Allowed addresses are 1 
to 254 and there should not be controllers with the same address on the 
same line. Address 255 can be used by the Master to communicate with all 
connected devices without knowing their addresses (broadcast mode), whi-
le with address 0 all devices receive command, but no answer is expected. 
ATR421 can introduce an answer delay (in milliseconds) to Master request. 
This delay has to be set on parameter 81 
se.de. At each parameters modi 
cation, instrument stores values in EEPROM memory (100000 writing cycles). 
NB: Modi cations made to Words di erent from those described in the fol-
lowing table can lead to instrument malfunction.
Here below list of available addresses
RO = Read Only R/W = Read / Write WO = Write Only
Modbus 
address
Description
Read 
Write
Reset 
value
0 Device type RO 210
1 Software version  RO FLASH
5 Slave address R/W EEPROM
6 Boot version RO FLASH
50 Automatic addressing WO -
51 Installation code comparison WO -
500
Loading Default values:
9999 restore all values except for cycles
9989 restore all values, cycles included 
RW 0
900
AI1 process (degrees with tenths of degree for 
temperature sensors; digits for linear sensors).
RO -
901
AI2 process (feedback potentiometer-Ohm/10)
RO -
902 Valve position – 0…100. RO -
1000
Process (degrees with tenths of degree for 
temperature sensors; digits for linear sensors).
RO -
1001 Process with decimal point selection.  RO -